But about 20 percent of the total weight of rice is made up of inedible husks, and a group of South Korean researchers wants to make good use of this waste product. They want to turn it into silicon. Their work was published this week in the Proceedings of the National Academy of Sciences.

Silicon is most famous for its use in semiconductors, but as the demand for batteries for smartphones and hybrid cars ramps up, researchers are hoping to use it to replace graphite in the anodes of lithium-ion batteries. Finding a cheaper source for silicon – such as rice husks – could help make these improved batteries more cost effective.

Waste husks are also used for other purposes, such as making bricks and fueling cooking stoves. But Jang Wook Choi, one of the researchers behind the paper, doesn't think that converting the husks into silicon will cause a disruption for other uses.

"The economics of it I think is going to be doable," Choi says. "The total amount required for batteries is much smaller than the amount of rice husks generated during de-seeding. So the supply is going to be much greater than what is required for silicon batteries."

The researchers extracted silica from the husks using heat and acid, and then converted the silica to silicon and used it in lithium batteries. They found that these batteries were more efficient than batteries made with traditional silicon alloys.